Dressing attachment for hob-grinding machines and method of dressing grinding wheels



Oct. 9; '1 928. v 1,686 802 FOR nos GRINDING MACHINES AND usmon OFnmassme GRINDING vmmans' J. EDGAR DRESSING ATTACHMENT Original FiledJuaa 28, 1916 INVENTDR JOHN E DEAR M424 lazh.

ATTY5.

Patented Oct. 9 1928.

UNITED STATES PATENT OFFICE.

JOHN EDGAR, OF ROCKFORD, ILLINOIS, ASSIGNOR TO BARBER-COLMAN COMPANY, OFROCKFORD, ILLINOIS, A CORPORATION OF ILLINOIS.

DRESSING ATTACHMENT FOR HOB-GRINDING MACHINES AN D METHOD OF DRESSINGGRINDING WHEELS.

Driglnal application filed June 28, 1916, Serial No. 106,339. Dividedand this application filed March 18,

1923. Serial No. 625,939

106,339, filed June 28, 1916of which this application is a division-Ihave shown a grinding machine of the type to which this The inventionpertains to the art of grinding machines such, for example, as thoseemployed in grinding the form of hobs; and the invention has particularreference to a means for dressing the grinding wheels employed in suchmachines.

The object of the invention is to provide a dressing attachment of athoroughly practical character which is capable of producing aperipheral grinding face for the wheel of a contour corresponding to thecontour to be imparted to the hob teeth.

A more specific object of the invention is to provide a supporting meansfor adressing 1 tool by which the latter may be moved in a plane passingthrough the axis of the grinding Wheel, in combination with means forguiding the tool to move so as to impart the desired form to thegrinding surface.

The objects of the invention thus generally stated, together with otherand ancillary advantages, are attained by the construction andarrangement illustrated in the accompanying drawings forming parthereof. While only one form of the invention is illustrated, it iscontemplated that various changes in the form, construction andarrangement of the parts may be made by those skilled in the art withoutdeparting from the spirit and scope of the invention as expressed in theappended claims.

In the drawings, Fig. 1 is a horizontal sectional view illustrating themeans for rotatably supporting the grinding wheel with respect to a hobbeing ground. Fig. 2 is a fragmentary side elevational view of myimproved dressing attachment and illustrating the manner in which it issupported in the grinding machine. Fig. 3 is a front view of the same.Fig. 4 is a fragmentary vertical sectional view through the lower end ofthe supporting means for the dressing tool, the view being taken on anenlarged scale to illustrate details of construction. Fig. 5 is a planview of the templet and its supporting frame for guiding the dressingtool carrier, the latter being shown in section. Fig. 6 is a detail viewillustrating the dressing operation. Fig. 7 is a fragmentary elevationalview showing a detail of construction.

In my copending application Serial No.

invention is capable of application.

Said

machine. comprises a bed (not herein shown upon which is mounted a slide1 (Fig. 2

carrying the head stock and the tailstock (not shown) between which isrotatably supported in horizontal position the hob A to be ground. Thetail stock is removably mounted on a guide 6 on the slide 1.

B indicates a grinding wheel which is rotated at a high speed in adirection opposite of rotation of the hob A.

to the direction lines in Fig. 1. The axis of the frame 93 intersectsthe axis of the hob at a right angle,

and when grinding the hob, tersection of the pitch line contact of thehob and the g in the axis of the frame 93.

the point of inand the line of rinding wheel is I The frame 93 ispivoted upon the carriage 82 by means of a shaft 94 mounted at oppositeends in spaced bearings 95 and 96. The

latter is rigid with the carriage, and the former is carried by avertical elongated member 97 rising from the carriage.

The

frame 93 is arranged to be held against swinging movement by means of ascrew 98 mountedin a threaded opening 99 in the frame and adapted toextend through either of two diametrically opposite curved slots 100 inthe member 97.

The frame 93 occupies a horizontal position when the grinding wheelwhich is being dressed is to be used in grinding the teeth of a spirallygashed hob; and occupies an inclined position when the being dressed isto be used grinding wheel for grinding a straight gashed hob. In thelatter instance the frame is inclined to the when grinding.

same degree as For the purpose of securing the frame in.

into either of two openings 102 provided atdiametrically opposite pointsin the upstanding member 97. The pin 101 is adapted to enter a hole 103in the frame 93, but is used only in setting the frame preparatory todressing the grinding wheel and at other times is withdrawn from theopening 103.

For facilitating the setting of the frame 93 at an angle correspondingto the angle of the thread of the hob, I provide a protractor ring 104mounted for rotation with the frame and having at its peripheral edgegraduations cooperating with a mark upon the stationary member 97 topermit the setting of the frame at any desired angle.

mounted in a sectional bearing The grinding wheel spindle 120 is mountedin a head 111 which is suitably mounted on the frame 93 for adjustmentrelative thereto as b means of nuts 117 on a screw stud 118 fixe to theframe 93. The spindle is con-' nected by a gear train 123-124 to acountershaft 125 which is driven by a bevel pinion 126 and crown gearteeth formed upon a pillley 127. The latter is rotatably mounted upon astud 128 and receives a belt 129 connected with a suitable source ofpower.

The dressing means is in the nature of an attachment which in practiceis mounted upon the slide 1 after the hob has been removed. Theattachment comprises a base 134 adapted to be seated upon the guide 6and having a notched depending lug 135 adapted to engage a positioningpin 136 (Figs. 2 and 3) fixed to the slide 69 upon which the grindingwheel carriage is mountedr By the aid of this lug and pin, the dressingattachment ma be properly located opposite the grinding w eel.

c The dressing attachment further comprises a bracket 137 having a base137 which is adjustable upon thebase 134 toward and away from thegrinding wheel by means of a screw-threaded rod 138 'secured to saidbracket and having a nut 139 thereon. Said nut rests in a recess formedin an upstanding projection on the base 134 and is grooved to formopposed shoulders engaging the opposite sides of said projection so asto hold the nut against longitudinal movement.

The dressing tool is carried by an arm140 the lower end of which isoffset or U-shaped and carries a pin or rod 141 which depends slidablythrough a ball 142 rotatably member 143 mounted in the base 137 of thebracket 137. Said bearing member is suitably secured within the upperenlarged portion of an aperture 134* through which the pin 141 pro'ects. At its lower end the pin is provided wit a. point 144 that restsin a concave recess 145 formed in a plate 145 secured to the base 137'.

The upper end of the arm 140 is arranged to be guided by a templet 147mounted upon a frame 148. To coact with this templet the upper portionof the arm is shaped to form a knife edge 146 and the outline of theworking portion of the templet is such that it corresponds to theoutline to be imparted to the sides of the teeth of the hob. The frame148 is rigid with and constitutes a part of the bracket 137, and is soconstructed as to permit the ready removal and replacement of thetemplet. As indicated by the broken lines in Fig. 5 the templet maybe'secured in the frame in either of two positions corresponding to thetwo horizontal positions of the knife edge 146. To assist in locatingthe point of the tool in this median line I provide flattened pins 153and-154 above and below the dressing tool against which pins a straightedge may be placed to serve as a guide in positioning the tool.

The curvature of the socket 145 is such that as the arm is oscillatedand moved along the edge of the templet 147, the arm will be moved upand down sufliciently to cause the dressing tool to move in a horizontalplane while tracing the contour of the surface to be ground upon theteeth of the hobs.

In dressing a grinding wheel the aim is to form the grinding face insuch a way that when the wheel axis is adjusted to correspond to thethread angle of the hob teeth, racktooth-shaped cutting faces will beproduced on the hob. To obtain this result in dressing a wheel which isto be used for grinding hobs having straight flutes or gashes, that isto say, gashes parallel to the axis of the hob, the frame 93 carryingthe grinding wheel to be dressed is secured in a position inclined tothe same degree as when grinding such a hob, the axis 120 of the wheelbeing then in a plane normal to the hob helix. On the other hand, whendressing a wheel that is to be used for grinding the teeth of a spirallygashed hob, the frame 93 is secured in a horizontal position, the axis120 of the wheel the hob when in position to be ground. In both cases,the same template is employed. When the wheel is being dressed it is ingrinding position, save that the frame 93 is horizontal when the wheelis bein dressed for use ingrindingaspirallygashed ob. The

through the center of the ball 142 and the D .being then in the sameplane as the axis of i point of intersection of the pitch line of thehob and the contour of the wheel is in the axis of the frame 93, as whengrinding.

and a dressing tool carrier comprising an I arm having a dressing toolthereon, the lower end of said arm being mounted on the second base toturn on an axis substantially coincident With the point of the dressingtool, said arm being adapted to slide along said templet to guide thedressing tool carried thereby in a predetermined path with respect tothe peripheral surface of the grinding wheel.

2. In a grinding machine, the combination of means for rotatablysupporting a grinding wheel, a dressing attachment comprising a carrierhaving a dressing point and a depending supporting pin, a ball slidablyengaging said pin, a bearing in which said ball is mounted, a bearingplate having a concave upper surface in which said pin is adapted toengage, and means for guiding the carrier in its swinging movements, thecurvature of said concave surface being such that the dressing pointalways moves in the same plane.

3. The combination of means for supporting and rotating a grindingwheel,'a carrier pivoted at one end and also free to turn on an axisextending longitudinally of the carrier, a dressing tool on the carrierhaving its point located approximately in said axis, and means formodifying the swinging movements of the carrier and thereby of the.dressing tool to cause the latter to travel in a plane.

4. The combination of a pivoted frame. a grinding wheel carried by theframe, the active portion of said wheel being in the axis of the frame,a dressing tool, and means for moving said tool in the plane of theactive portion of said wheel.

5. The combination with means for rotatably supporting a grinding wheel,of a dressing attachment comprising an arm having a dressing toolthereon and having a universal pivotal support, a support with whichsaid arm slidably engages shaped to cause said tool to travel in ahorizontal plane in the swinging movements of the arm, and a templet forguiding said tool'in its movements.

6. The combination of a pivoted frame, a grinding wheel rotatablysupported in said frame, said frame being adjustable through an arc ofapproximately 180 degrees, and means for dressing the grinding wheelcomprising a tool carrier and a stationary frame having a templet withwhich said carrier is arranged to coact in guiding the movements of thetool, said templet being reversible to conform to the positions of saidframe and hence of the grinding wheel.

7. The method of dressing a grinding wheel which is to be used forgrinding spirallygashed hobs to produce correct tooth outlines,comprising positioning a grinding wheel with its ax s in the same planeas the axis of a hob when in position to be ground, the line of contactof the wheel with a hob so posi tioned intersecting the pitch line ofthe hob in an axis on which the grinding wheel may be adjusted intogrinding position, and moving a dressing point through the correct toothoutline in contact with the grinding wheel to dress the same.

8. The method of dressing a grinding wheel which is to be used forgrinding straightgashed hobs to produce correct tooth outlines,comprising placing a grinding wheel in grinding position with its axisin a plane normal to the helix of a hob when supported in position to beground, the line of contact of the wheel with a hob so positionedintersecting the pitch line of the hob in an axis on which the grindingwheel may be bodily swung through 180"v into position to grind the otherside of the teeth, and moving a dressing point through the correct toothoutline in contact with the grinding wheel to dress the same.

In testimony whereof, I have hereunto affixed my signature.

JOHN EDGAR.

